The present invention relates to a tank wagon for agricultural use. More particularly, the invention relates to a tank wagon, such as an anhydrous ammonia tank wagon, provided with a pivotable coupling assembly having a pivot axis that is offset from the front axle of the tank wagon.
Anhydrous ammonia is a standard liquid fertilizer typically applied by farmers prior to spring planting season or during the initial growth stage of the crop. Anhydrous ammonia is usually stored in bulk by dealers and transferred to 1,000 gallon or 1,450 gallon tanks which are secured to tank wagons for use by farmers. Farmers often participate in a rental program with dealers for seasonal use of the tank wagons.
In the usual arrangement, the farmer travels to the dealer's premises to pick up the fully-loaded tank wagon and uses his own pick-up truck or other vehicle to tow the tank wagon back to the farm. Thus, the tank wagon must be designed for safe operation at the road speeds set by law for operation of such vehicles.
Of course, upon reaching the farm, the tank wagon will be subjected to the rugged conditions typical of tillage operations. The tank wagon will normally be attached to an NH.sub.3 /liquid applicator (for example, a pull-type swath applicator) and towed across the field to be fertilized. A farmer having considerable acreage to fertilize may need to make frequent trips between the farm and the dealer's premises to refill the tank.
Because tank wagons are typically distributed on a rental basis, they should be adaptable to accommodate varying row widths in the fields to be fertilized. Some farmers plant in 30 inch row spacings, while others prefer 36 or even 38 inch spacings. Where fertilizer is to be applied during the initial growth stage of the crop, tank wagon adaptability is required.
One problem frequently associated with some tank wagons is their tendency to roll over when turned sharply. It is recognized that conventional fifth wheel tank wagons may overturn if the front axle of the wagon is pivoted sharply relative to the load.
One attempt to solve this problem involves a design which abandons the fifth wheel arrangement entirely in favor of an automotive steering arrangement. See DMI.RTM. Form No. 1598A5 (DMI.RTM. Auto-Steer Tank Wagon). In the automotive steering arrangement, only the front wheels, not the front axle, pivot relative to the load when the tank wagon is turned.
Another longstanding problem with tank wagons is their tendency to sway or fishtail when pulled at normal road speeds with a pickup truck or other tow vehicle. Since the problem is more pronounced at higher speeds, the farmer may be forced to tow the wagon at less than normal road speeds set by law for operation of vehicles of this type. This may translate into a significant time loss for a farmer who must make frequent trips between the farm and the dealer's premises, and may also create traffic problems. The problem is also especially noticeable when the farmer tows both a first tank wagon and a second tank wagon hitched to the rear of the first tank wagon. It would thus be desirable to provide a tank wagon designed to minimize both the rollover and the swaying problems while providing ample load-bearing support and adaptability as required of such vehicles.
According to the present invention, an agricultural tank wagon is provided. The wagon is adapted for attachment to a tow vehicle such as a pickup truck or an agricultural implement. The tank wagon comprises front running gear, rear running gear, a first coupling assembly pivotably coupling the rear running gear to the front running gear, a wagon tongue for attachment to the tow vehicle, and a second coupling assembly pivotably coupling the wagon tongue to the front running gear. The front running gear includes a front axle defining a central axis of rotation. The rear running gear cooperates with the front running gear to support the tank. The first coupling assembly operates to pivot the rear running gear relative to the front axle about a first pivot axis that is offset from the central axis of rotation. The second coupling assembly operates to pivot the wagon tongue relative to the front axle about a second pivot axis lying in substantially parallel offset relationship with the central axis of rotation.
In accordance with one preferred aspect of the invention, the first coupling assembly includes a first plate affixed to the front axle. The first plate includes a first extended portion extending forward of the front axle and being formed to include a first opening aligned with the first pivot axis. The first coupling assembly further includes a second plate including a second extended portion extending forward of the front axle and being formed to include a second opening aligned with the first pivot axis. The first coupling assembly also includes a first pivot pin extending through the first and second openings along the first pivot axis to place the second plate in substantially overlapping pivoting relationship with the first plate.
In accordance with another preferred aspect of the invention, the wagon further includes a front tank-supporting bolster. A third coupling assembly pivotably couples the front tank-supporting bolster to the second plate at a location rearwardly offset from the first pivot axis. The third coupling assembly pivots the front tank-supporting bolster relative to the second plate about a third pivot axis transverse to the central axis of rotation.
In accordance with another preferred aspect of the invention, the second coupling assembly includes at least one pivot pin. The pivot pin is aligned along the second pivot axis and is positioned forward of the front axle and the first pivot axis.
Further in accordance with the present invention, an agricultural tank wagon adapted for attachment to a tow vehicle comprises first means for supporting a tank, second means for supporting the tank, first means for pivotably coupling the second supporting means to the first supporting means, a wagon tongue for attachment to the tow vehicle, and second means for pivotably coupling the wagon tongue to the front axle. The first supporting means includes a front axle defining an axis of rotation. The first coupling means operates to pivot the second supporting means about a first pivot axis that is offset from the axis of rotation of the front axle. The second coupling means operates to pivot the wagon tongue relative to the front axle about a second pivot axis lying in substantial parallel offset relationship to the axis of rotation of the front axle.
Further in accordance with the present invention, an agricultural tank wagon adapted for attachment to a tow vehicle comprises first means for supporting a tank, second means for supporting a tank, and means for pivotably coupling the second supporting means to the first supporting means.
The second supporting means includes a pole having a forward end and a rearward end. A rear axle is attached to the pole at the rearward end.
The coupling means includes a first plate affixed to the front axle, the first plate having an extended portion extending forward of the front axle and being formed to include a first opening. The coupling means also includes a second plate attached to the pole at the forward end. The second plate includes a second extended portion formed to include a second opening. The coupling means further includes a pivot pin extending through the second opening and the first opening to place the second plate in substantially overlapping pivoting relationship. The pivot pin also defines a first pivot axis that is forwardly offset from the axis of rotation of the front axle so that the pivot pin is isolated from compressive loading forces applied by the tank.
Additional objects, features, and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of preferred embodiments exemplifying the best mode of carrying out the invention as presently perceived.